Method of zinc coating ferrous metal



July 3, 1928. 1,675,546-

J. G. FIVTZ GERALD METHOD OF ZINC GOATING FERROUS METAL Filed March so,1925 Patented July 3, 1928.

UNITED STATES y 1,615,646 lrA'rErrr-I OFFICE.

`JOSEPH G. FITZ GERALD, OF CANTON, OHIO, ASSIGNOB, BY DIRECT AND MESNEASSIGN- MENTS, TO CENTRAL ALLOY STEEL CORPORATION, OF CANTON, OHIOQACORPORA- 'rIoN 0F NEW Yom; i

nia'rnon oFlzINc coATKINe rannous METAL Application filed Harel! 30,1925.v Serial No. 19,381.. l

The invention relates to the process of coating ferrous metal with afilm of zinc, which is commonly called` galvanizing when applied to thezinc coating of steel or iron sheets. One object of the improvement isto cause such a coating to adhere so tightly to the ferrous metalthat'it will not become detached or scale therefrom during bending,breaking or deep drawing operations; and another object of theimprovement is to so control the crystallization of the zinc coating asto present a uniform velvety gray `frosted appearance to the surface ofthe sheet.

Ordinary galvanized sheets present a bright surface of large granularspangles variegated in appearance and of different sizes and shapes,which may have so little adhe.

ordinarily used in a .galvanizing process, be-v fore it ispassed-through molten spelter, the pores of the ferrous metal will openup to such an extent that when it is bathed in the molten spelter, thesame will find its way into the pores and amalgamate more intimatelywith the ferrousbase; and the same super-heating of the sheet, and theresultingsuperheatin of the spelter, results in a thinner coatin g o thesame being applied'to the sheet. I have, also discovered that theadhesion of such a coating is increased by a slow and gradual cooling ofthe same,` extended through af considerable period of time; and thattllis treatment also reduces the size, the appearance, and the characterof the zspangles, which.'may be reduced to-such a. minute size as topresent a uniform velvety gray frosty appearance, instead of the brightflaky appearance4 of the ordinary .galzanized s eet. v

By thus superheating the sheet in lead and spelter baths successively,and then control ling the degree and the rate of the cooling conditions,I lhave found that a galvanized sheet can be produced with a coating sotight as to adhere, without scalin during forming operations, orwhen sujected Ato high temperatures and also with a uniform velvety graysurface which is desirable for spe'- elevation section, somewhatdiagrammatic,

of apparatus which may be used for carrying out the improved process.Such apparatus may include al cleaning tank A, a galvanizing pot BLw-ith a hood C therefor, a heat maintaining and cooling tunnel D,finishing rolls E, leveling rolls'Fand' a porcupinev cooling ,ta-ble G.v

vSteel or iron `sheets may be cleaned for galvanizing by a weak solution2 of hydrochloric or muriat-ic acid in the tank'A, and then carriedbyrolls 3 between'guides 4 and 4 to feed-in rolls 5, which. direct themdownward through a salammoniac flux 6 in a trough' 7 directly into abath of molten lead 8, all in accordance with common and well knownpractice.

The molten lead' bath may have a'depth of some thirty or thirty-sixinches on top of which floats a layer of molten spelter 9, which ma bemolten zinc, together with 'such additionsof tin, antimony, and thelike,

as may be desired, according to the particular character of thecoatingdesired. It will be understood that the flux trough 7 extends downwardinto the molten lead, so that the sheets vpass through the lfluir intothe lead without coming into contact with the'spelter. For the purposeof the present invention, the molten lead is maintained at a temperature.of from 850 to 950 F. preferably about 900 F., which is from 50 to 100higher than common' -galvanizing practice; the pu ose of which is notonly to su rheat the bo y of the sheets before passing the same throughthe spelter, but to open or enlarge the pores of the ferrous metal sothat the s Iter` and iron will amalgamate more comp etely. y

Furthermore, the superheating of the lead serves to superheat thespelter floating thereon to a higher temperature than in ordinarypractice, and melts the, same to a thinner liquid, which not onlyamalgamatesv more readily with the ferrous metal, but produce a .throughthe molten lead and upward sheets are directed by guides 13 and 13 on anendlessiconveyor 14, which details of the apparatus may all be inaccordance with common practlce. The tunnelD may be of an o(pen or amuflle type, and may be heated by irect or indirect means, as forinstance electric coils, or some form of fuel, and as shown may beheated by gas flames flowing from suitable apertures or slots intransverse tubes, so that the flames may impinge the sheet if desired.The heating means are arranged so as to maintain the temperature in theend portion of the tunnel adjacent to the galvanizing pot, and so thatthe temperature in the tunnel will gradually decrease toward the otheren ereof; the purpose of the tunnel being to control the cooling of thehot coated sheets so that the same will be gradual and will extendthrough a considerable ing'of the hot coated sheet, to produce a periodof time. The preheatin of the sheet and the spelter by the super catedlead bath, not only more completely amalgamates the spelter coating withthe ferrous body of the sheet,

`but with` the slow and gradual cooling thereof so modifies the granularstructure of the rcoatingl asA to not only change the appearance tereofsas descrlbed, but also increases the adhesion thereof to the'bodof the sheet, so that the same can be sharply or drawn deeply or subjectto high temperature without detaching or scaling the 'coating from thebody of the' sheet.

vThe finishing rolls E may be ordinary cold rolls for compressing thecoating on and into the' ferrous metal and producing a smooth finishthereon, or wire scratchingrollsfor'making al satin finish, or brushburnshing' rolls for making abright finish,

`in accordance with the commonuse of these and other liinds of finishingrolls.

The ordinary, flattening rolls F may be used vfor straightening a vbent,Yor buckled sheet and a porcupine cooling table'G may be used for finaly cooling the ysheets .for manually handlin the same for delivering themat the end o the continuous processes described herein.- A I s.

I claims. .A l,

1.' The "method of zinc coating .ferrous metal, which' consists inheating the metal to be coated to from' 850". to 950 F. and

-then coating itin a molten spelter bath to produce a tlghtcoat.

-2.A The 'method of zinc 4coating ferrous metal, which consists inheating `the metal to be'coated in a molten lead bath to from ent siste-in passing metal, which consists in heating the'metal, then coating itin a molten spelter bath, and then controlling the cooling of the hotcoated sheet, to produce a tight coat of the desired character andappearance. f4. The method of zinc coating ferrous metal, which consistsin heating the metal to be coated to from 850 to 950 F., then coatin itin a molten spelter bath andthen contro ling the cooling of the hotcoated sheet, lto produce a tight coat of the desired character andappearance.

5. The method'of zinc coating ferrous metal, which consists in heatingthe metal in a molten lead bath, then coating it in a molten spelterbath, and then controlling the cooling of the hot coated sheet, -toproduce a tight coat of the desired character and a earance. p

' 6. 'Flic method of zinc coating ferrous metal, which consists in'heating the metal to be coated in a molten lead bath to from 850 to 950F., then coating it in a molten spelter bath, and then controlling thecoolling the cooling of the hot coated metal by predetermined gradationsof temperature to produce the desired character and appearance of thecoating.

8. The methbd of zinc coating a ferrous metal, which consists in coatingthe metal in a molten spelter bath, and then controlling the temperatureof the cooling of the hot coated metal to produce the desired characterand ap arance of the coating.

9. The method)e of zinc coating ferrous metal, which consists in coatinthe metal in a moltenA spelter bath, and t en controllin the time andthe temperature of the coo ing of the hot coatedl metal to produce thedesired character and appearance o f the coatin 10. I netal, whichconsists in coating the metal in a molten spelter bath, then controllingthe cooling ofthe hot coated metal by predetermined dations oftemperature to pro- 'duce the', esired chracter and appearanceofthecoating, and then finishing and flattening the sheet, al1 by acontinuous process.

11,. The method of 'treating galvanized' sheets immediately followin theexit of the latter from the galvanizing ath, which con# the sheetsthrough a zone of applied heat in which they are permitted to cool tionsof temperature.

v In' testimony that I claim theiabove I have hereunto subscribed mname.JOSEPH G. F Z GERALD.

gradually by predeterminedv 'gra'da-I lhe-vmethod of zinc coatingferrous

